New Window Flashing Products Prove Challenging, According to Building Risk Expert Stan Luhr

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Leakage claims continue despite widespread use of newer flexible flashing systems designed to eliminate leaks, but building risk expert Stan Luhr of AxisPointe believes more attention should be given to the installation rather than the products to cure complex waterproofing challenges

Frustration and cost. When window flashings fail, the results are catastrophic for the homeowner and builder.

Recessed windows should be treated like they are mini-roof systems, since water doesn’t know the difference...

Window leakage claims continue to plague homeowners and frustrate builders, despite wide adoption of more expensive self-adhered flashing (SAF) products specifically designed to prevent such leakage, according to nationally recognized forensic expert Stan Luhr.

The problem isn’t with the new products' flexibility or adhesive qualities, according to Luhr, CEO of Utah-based AxisPointe, a risk management services provider. Luhr has investigated hundreds of window failures across the country, and claims that installers place too much faith on the products. “It’s all in how the products are being installed,” says Luhr.

Dozens of SAF products are on the market, including brands from Grace, DuPont, Fortifiber, Protecto Wrap and others. Luhr says the products work well when installed properly, but other factors must be considered when trying to make a building weatherproof, particularly in recessed window designs common in the west.

“A recessed window should be treated like a roof with a window opening very close to the deck surface, and that is why it is problematic for some builders,” Luhr said. Luhr’s forensic business includes testing windows and solving problems for builders and insurers before they get out of hand. When problems go unresolved, litigation often follows, leading to frustrated homeowners and expensive lawyer battles.

Luhr claims that most leaks occur due to the following reasons, which can be easily corrected during installation:

Improper clearance to window. Recessed windows, particularly in stucco designs, often lack sufficient room to allow the SAF products to terminate vertically, above the finished stucco or brick sill. This results in a ‘bathtub effect’, trapping water in the system where it finds its way through the slightest hole and into the building. Luhr recommends elevating the rough window sill at least 4-inches above the horizontal shelf to allow sufficient vertical termination of the membrane and clearance to the window sill product. Window offsets less than 6-inches should require the window to be installed after the sill is waterproofed.

Leakage at Flashing Product Lap Joints. SAF products stick together very well, giving a false impression that a seam is entirely waterproof when it isn’t. Luhr says that the primary leakage is at the recessed window sill, where multiple pieces are joined together or when wrinkles occur at splices. When products are installed at inside corners and 90-degree joints, small openings can occur which allow water to travel through.

Complex Inside Corners. Many popular SAF products do not flex and stretch around three-dimensional corners, requiring the SAF to be cut and spliced. At inside recessed corners, Luhr insists that a folded corner—not a spliced corner—should be installed. Folded corners are created by folding the product into the dimensional shape which results in a completely waterproof joint.

Outside Corners. SAF products must be cut and spliced to lay flat, creating a pinhole where no protection exists. Luhr says that despite manufacturers suggesting use of a corner piece (often called a “bowtie”), leakage still occurs. Luhr prefers products that can completely cover the outside corner, such as DuPont’s FlexWrap™ which stretches and can be installed around corners without cutting.

Inadequate Slope at Sills. SAF products are considered waterproof when perfectly installed, but few installations are perfect. Luhr recommends providing positive slope under the flashings to promote rapid drying and movement of water. The minimum recommended slope is ½-inch per foot to keep water from ponding within the system. For level sills, perfection is required.

The Self-Sealing Myth. In Luhr’s investigations of thousands of windows, he concludes that SAF products cannot be trusted to self-seal around fasteners used to secure lath and other components. “We would never allow hundreds of nails to penetrate a built-up roof system, which is 10 times thicker than these SAF products,” Luhr said. “Why do we allow lath fasteners on the flat portions of recessed sills?” He recommends prohibiting all fasteners on the horizontal portion, securing the lath at least 2-inches higher than the horizontal shelf and only on the vertical sides. Luhr argues that stucco routinely spans studs up to 24-inches apart, and there is no need to fasten lath that is only spanning a few inches horizontally.

Missing Backing. “SAF products do not seal around penetrations unless the fastener is secured into solid backing where it cannot move,” says Luhr, who adds that he often proves this simply by pushing fasteners into the SAF products and filling with water to watch them leak.

“Recessed windows should be treated like they are mini-roof systems, since water doesn’t know the difference between a horizontal stucco shelf and a flat roof,” Luhr said. “Yet we think because they are on a wall, we don’t have to take the same care of providing backing, slope and waterproofing as we do on a roof—and that is where we are going wrong.”

Luhr admits that installing SAF products is complicated. He has provided architects with a sequence of details to illustrate his installation method that has proven successful with his clients. “An even better solution is to transition to liquid membranes that incorporate a reinforcing scrim,” but Luhr says, “These are just coming into the market place and few builders seem comfortable smearing a sour cream consistency product on their recessed framing.” Liquid membranes will eliminate splicing and seam leaks, and can be more easily inspected that multiple flashing pieces for integrity.

Luhr prompted manufacturers to develop liquid membranes and tested several formulations to help create a product that builders can rely on that is easily applied and cheaper to install. Recently ProtectoWrap and DuPont have announced liquid membrane products and Luhr believes the market will transition to liquid membrane flashing once builders recognize the benefits, cost savings and risk reduction.

What can builders do to prevent leakage? Consider the following if recessed window openings are planned on your project:
Be sure to detail the installation, product and sequence so that everyone is on board with the installation method
Build a full scale mock-up and water test the window, particularly for new trade partners or if new products are considered
Use only one manufacturer’s brand—don’t intermix flashing systems and components
Verify that the products are compatible with the window manufacturer’s guidelines
Provide sufficient room between the window fin and framing
Prohibit lath fasteners on any non-vertical surfaces, even when good slope exists
Consider the use of reinforced mesh and liquid membrane systems to reduce defects caused by miss-laps, wrinkles and complex corner breaches.

About AxisPointe
AxisPointe partners with home builders and contractors with technology solutions to streamline the construction process and eliminate risk. AxisPointe’s HomeProfile® document management software has been employed on thousands of homes by leading builders. AxisPointe’s platform of services includes project quality assurance, safety and control systems, project document storage and archiving, customer service management, insurance certificate management, post-warranty claims and litigation management systems.
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